Conveyor Lubricant And Method For Transporting Articles On A Conveyor System - Patent 6495494

Document Sample
Conveyor Lubricant And Method For Transporting Articles On A Conveyor System - Patent 6495494 Powered By Docstoc
					


United States Patent: 6495494


































 
( 1 of 1 )



	United States Patent 
	6,495,494



 Li
,   et al.

 
December 17, 2002




 Conveyor lubricant and method for transporting articles on a conveyor
     system



Abstract

The passage of a container along a conveyor is lubricated by applying to
     the container or conveyor a mixture of a water-miscible silicone material
     and a water-miscible lubricant. The mixture can be applied in relatively
     low amounts and with relatively low or no water content, to provide thin,
     substantially non-dripping lubricating films. In contrast to dilute
     aqueous lubricants, the lubricants of the invention provide drier
     lubrication of the conveyors and containers, a cleaner conveyor line and
     reduced lubricant usage, thereby reducing waste, cleanup and disposal
     problems.


 
Inventors: 
 Li; Minyu (Oakdale, MN), Lokkesmoe; Keith Darrell (Savage, MN) 
 Assignee:


Ecolab Inc.
 (St. Paul, 
MN)





Appl. No.:
                    
 09/596,599
  
Filed:
                      
  June 16, 2000





  
Current U.S. Class:
  508/206  ; 508/208; 508/215; 508/433; 508/579; 508/583
  
Current International Class: 
  C10M 107/50&nbsp(20060101); C10M 111/04&nbsp(20060101); C10M 105/24&nbsp(20060101); C10M 105/00&nbsp(20060101); C10M 111/00&nbsp(20060101); C10M 107/00&nbsp(20060101); C10M 111/02&nbsp(20060101); C10M 105/14&nbsp(20060101); C10M 171/00&nbsp(20060101); C10M 173/02&nbsp(20060101); C10M 173/00&nbsp(20060101); B65D 23/08&nbsp(20060101); B65D 23/00&nbsp(20060101); C10M 107/38&nbsp(20060101); C10M 173/02&nbsp(); C10M 139/00&nbsp(); C10M 141/12&nbsp()
  
Field of Search: 
  
  



 508/206,208,214,215
  

References Cited  [Referenced By]
U.S. Patent Documents
 
 
 
3011975
December 1961
Nitzsche et al.

3213024
October 1965
Blake et al.

3664956
May 1972
Messina et al.

3981812
September 1976
Zletz

4149624
April 1979
Douty et al.

4162347
July 1979
Montgomery

4248724
February 1981
MacIntosh

4289671
September 1981
Hernandez

4324671
April 1982
Christian et al.

4436200
March 1984
Hodlewski et al.

4652386
March 1987
Alberts et al.

4719022
January 1988
Hyde

4828727
May 1989
McAninch

4929375
May 1990
Rossio et al.

5009801
April 1991
Wider et al.

5062979
November 1991
Scharf et al.

5073280
December 1991
Rossio et al.

5160646
November 1992
Scheld

5174914
December 1992
Gutzmann

5182035
January 1993
Schmidt et al.

5191779
March 1993
Imaja et al.

5334322
August 1994
Williams, Jr.

5352376
October 1994
Gutzmann

5474692
December 1995
Laufenberg et al.

5486316
January 1996
Bershas et al.

5549836
August 1996
Moses

5559087
September 1996
Halsrud et al.

5565127
October 1996
Laufenberg et al.

5663131
September 1997
Winicov et al.

5672401
September 1997
Anglin et al.

5681628
October 1997
Niederst et al.

5688747
November 1997
Khan et al.

5747430
May 1998
Matsushita et al.

5863874
January 1999
Person Hei et al.

5869436
February 1999
Lindman

5925601
July 1999
McSherry

5935914
August 1999
Theyssen et al.

6207622
March 2001
Li et al.



 Foreign Patent Documents
 
 
 
1157456
Nov., 1983
CA

0 359 330
Mar., 1990
EP

0 844 299
May., 1998
EP

1564128
Apr., 1980
GB

57003892
Jan., 1982
JP

06-136377
May., 1994
JP

10053679
Aug., 1996
JP

10059523
Mar., 1998
JP

9300742
May., 1993
NL

96/08601
Mar., 1996
WO



   
 Other References 

"The Alternative to Soap and Water for Lubricating Conveyor Lines," Food & Drink Business, pp. 35-36 (Jan. 1998).
.
Lubrication and Lubricants, Encyclopedia of Chemical Technology, vol. 15, pp. 463-517.
.
"A fracture mechanics approach to environmental stress cracking in poly(ethyleneterephthalate)," Polymer, vol. 39 No. 3, pp. 75-80 (1998).
.
Material Safety Data Sheet for Lubostar CP (May 3, 2000).
.
"Environmental Stress Cracking in PET Carbonated Soft Drink Containers," Eric J. Moskala, Ph.D., Eastman Chemical Company, presented at Bev Tech 98 (Savannah, GA).
.
"Environmental Stress Cracking Resistance of Blow Molded Poly(Ethylene Terephthalate) Containers," Polymer Engineering and Science, vol. 32, No. 6, pp. 393-399 (Mar. 1992)..  
  Primary Examiner:  McAvoy; Ellen M.


  Attorney, Agent or Firm: IPLM Group, P.A.



Claims  

We claim:

1.  A method for lubricating the passage of a container along a conveyor, comprising applying a mixture of a water-miscible silicone material and a water-miscible lubricant to at least a
portion of the container-contacting surface of the conveyor or to at least a portion of the conveyor-contacting surface of the container.


2.  A method according to claim 1, wherein the mixture forms a substantially non-dripping film.


3.  A method according to claim 1, wherein the mixture can be applied without requiring in-line dilution with significant amounts of water.


4.  A method according to claim 1, wherein the mixture can readily be removed using a water-based cleaning agent.


5.  A method according to claim 1, wherein the mixture is formed without adding surfactants that cause environmental stress cracking in polyethylene terephthalate.


6.  A method according to claim 1, wherein the mixture comprises about 0.05 to about 12 wt. % of the silicone material and about 30 to about 99.95 wt. % of the water-micible lubricant.


7.  A method according to claim 1, wherein the mixture also comprises water or a hydrophilic diluent.


8.  A method according to claim 7, wherein the mixture comprises about 0.5 to about 8 wt. % of the silicone material, about 50 to about 90 wt. % of the water-miscible lubricant, and about 2 to about 49.5 wt. % of water or hydrophilic diluent.


9.  A method according to claim 1, wherein the silicone material comprises a silicone emulsion, finely divided silicone powder, or silicone surfactant.


10.  A method according to claim 1, wherein the silicone material comprises a silicone emulsion and the mixture comprises water.


11.  A method according to claim 1, wherein the water-miscible lubricant comprises a hydroxy-containing compound, polyalkylene glycol, copolymer of ethylene and propylene oxides, sorbitan ester or derivative of any of the foregoing.


12.  A method according to claim 1, wherein the water-miscible lubricant comprises a phosphate ester or amine or derivative of either of the foregoing.


13.  A method according to claim 1, wherein the water-miscible lubricant comprises glycerol.


14.  A method according to claim 1, wherein the mixture has a total alkalinity equivalent to less than about 100 ppm CaCO.sub.3.


15.  A method according to claim 14, wherein the total alkalinity equivalent is less than about 30 ppm CaCO.sub.3.


16.  A method according to claim 1, wherein the mixture has a coefficient of friction less than about 0.14.


17.  A method according to claim 16, wherein the coefficient of friction is less than about 0.1.


18.  A method according to claim 1, wherein the containers comprise polyethylene terephthalate or polyethylene naphthalate.


19.  A method according to claim 1, wherein the mixture is applied only to those portions of the conveyor that will contact the containers, or only to those portions of the containers that will contact the conveyor.


20.  A method according to claim 1, wherein the mixture exhibits shear thinning while being applied and is non-dripping when at rest.


21.  A lubricated conveyor or container, having a lubricant coating on a container-contacting surface of the conveyor or on a conveyor-contacting surface of the container, wherein the coating comprises a mixture of a water-miscible silicone
material and a water-miscible lubricant.


22.  A conveyor or container according to claim 21, wherein the coating forms a substantially non-dripping film.


23.  A conveyor or container according to claim 21, wherein the mixture can be applied without requiring in-line dilution with significant amounts of water.


24.  A conveyor or container according to claim 21, wherein the coating can readily be removed using a water-based cleaning agent.


25.  A conveyor or container according to claim 21, wherein the mixture was formed without adding surfactants that cause environmental stress cracking in polyethylene terephthalate.


26.  A conveyor or container according to claim 21, wherein the coating comprises about 0.5 to about 8 wt. % of the silicone material, about 50 to about 90 wt. % of the water-miscible lubricant, and further comprises about 2 to about 49.5 wt. %
of water or hydrophilic diluent.


27.  A conveyor or container according to claim 21, wherein the silicone material comprises silicone emulsion, finely divided silicone powder, or silicone surfactant;  and the water-miscible lubricant comprises a hydroxy-containing compound,
polyalkylene glycol, copolymer of ethylene and propylene oxides, sorbitan ester or derivative of any of the foregoing lubricants.


28.  A conveyor or container according to claim 21, wherein the silicone material comprises silicone emulsion, finely divided silicone powder, or silicone surfactant;  and the water-miscible lubricant comprises a phosphate ester, amine or
derivative of either of the foregoing lubricants.


29.  A conveyor or container according to claim 21, wherein the coating comprises a silicone emulsion, glycerol and water.


30.  A conveyor or container according to claim 21, wherein the coating has a total alkalinity equivalent to less than about 100 ppm CaCO.sub.3 and the containers comprise polyethylene terephthalate or polyethylene naphthalate.


31.  A conveyor or container according to claim 30, wherein the total alkalinity equivalent is less than about 30 ppm CaCO.sub.3.


32.  A conveyor or container according to claim 30, wherein the containers comprise crystalline and amorphous surface portions and the coating contacts one or more crystalline surface portions but does not contact significant amorphous surface
portions of the container.  Description  

TECHNICAL FIELD


This invention relates to conveyor lubricants and to a method for conveying articles.  The invention also relates to conveyor systems and containers wholly or partially coated with such lubricant compositions.


BACKGROUND ART


In commercial container filling or packaging operations, the containers typically are moved by a conveying system at very high rates of speed.  Copious amounts of aqueous dilute lubricant solutions (usually based on fatty acid amines) are
typically applied to the conveyor or containers using spray or pumping equipment.  These lubricant solutions permit high-speed operation of the conveyor and limit marring of the containers or labels, but also have some disadvantages.  For example,
aqueous conveyor lubricants based on fatty amines typically contain ingredients that can react with spilled carbonated beverages or other food or liquid components to form solid deposits.  Formation of such deposits on a conveyor can change the lubricity
of the conveyor and require shutdown to permit cleanup.  Some aqueous conveyor lubricants are incompatible with thermoplastic beverage containers made of polyethylene terephthalate (PET) and other plastics, and can cause environmental stress cracking
(crazing and cracking that occurs when the plastic polymer is under tension) in plastic containers.  Dilute aqueous lubricants typically require use of large amounts of water on the conveying line, which must then be disposed of or recycled, and which
causes an unduly wet environment near the conveyor line.  Moreover, some aqueous lubricants can promote the growth of microbes.


SUMMARY OF THE INVENTION


The present invention provides, in one aspect, a method for lubricating the passage of a container along a conveyor comprising applying a mixture of a water-miscible silicone material and a water-miscible lubricant to at least a portion of the
container-contacting surface of the conveyor or to at least a portion of the conveyor-contacting surface of the container.


The present invention provides, in another aspect, a lubricated conveyor or container, having a lubricant coating on a container-contacting surface of the conveyor or on a conveyor-contacting surface of the container, wherein the coating
comprises a mixture of a water-miscible silicone material and a water-miscible lubricant.


The invention also provides conveyor lubricant compositions comprising a mixture of a water-miscible silicone material and a water-miscible lubricant.


The compositions used in the invention can be applied in relatively low amounts and do not require in-line dilution with significant amounts of water.  The compositions of the invention provide thin, substantially non-dripping lubricating films. 
In contrast to dilute aqueous lubricants, the lubricants of the invention provide drier lubrication of the conveyors and containers, a cleaner and drier conveyor line and working area, and reduced lubricant usage, thereby reducing waste, cleanup and
disposal problems. 

BRIEF DESCRIPTION OF THE DRAWING


FIG. 1 illustrates in partial cross-section a side view of a plastic beverage container and conveyor partially coated with a lubricant composition of the invention. 

DETAILED DESCRIPTION


The invention provides a lubricant coating that reduces the coefficient of friction of coated conveyor parts and containers and thereby facilitates movement of containers along a conveyor line.  The lubricant compositions used in the invention
can optionally contain water or a hydrophilic diluent, as a component or components in the lubricant composition as sold or added just prior to use.  The lubricant composition does not require in-line dilution with significant amounts of water, that is,
it can be applied undiluted or with relatively modest dilution, e.g., at a water:lubricant ratio of about 1:1 to 5:1.  In contrast, conventional dilute aqueous lubricants are applied using significant amounts of water, at dilution ratios of about 100:1
to 500:1.  The lubricant compositions preferably provide a renewable coating that can be reapplied, if desired, to offset the effects of coating wear.  They preferably can be applied while the conveyor is at rest or while it is moving, e.g., at the
conveyor's normal operating speed.  Preferably the lubricant coating is water-based cleaning agent-removable, that is, it preferably is sufficiently soluble or dispersible in water so that the coating can be removed from the container or conveyor using
conventional aqueous cleaners, without the need for high pressure, mechanical abrasion or the use of aggressive cleaning chemicals.  The lubricant coating preferably is substantially non-dripping, that is, preferably the majority of the lubricant remains
on the container or conveyor following application until such time as the lubricant may be deliberately washed away.


The invention is further illustrated in FIG. 1, which shows a conveyor belt 10, conveyor chute guides 12, 14 and beverage container 16 in partial cross-sectional view.  The container-contacting portions of belt 10 and chute guides 12, 14 are
coated with thin layers 18, 20 and 22 of a lubricant composition of the invention.  Container 16 is constructed of blow-molded PET, and has a threaded end 24, side 25, label 26 and base portion 27.  Base portion 27 has feet 28, 29 and 30, and crown
portion (shown partially in phantom) 34.  Thin layers 36, 37 and 38 of a lubricant composition of the invention cover the conveyor-contacting portions of container 16 on feet 28, 29 and 30, but not crown portion 34.  Thin layer 40 of a lubricant
composition of the invention covers the conveyor-contacting portions of container 16 on label 26.


The silicone material and hydrophilic lubricant are "water-miscible", that is, they are sufficiently water-soluble or water-dispersible so that when added to water at the desired use level they form a stable solution, emulsion or suspension.  The
desired use level will vary according to the particular conveyor or container application, and according to the type of silicone and hydrophilic lubricant employed.


A variety of water-miscible silicone materials can be employed in the lubricant compositions, including silicone emulsions (such as emulsions formed from methyl(dimethyl), higher alkyl and aryl silicones; functionalized silicones such as
chlorosilanes; amino-, methoxy-, epoxy- and vinyl-substituted siloxanes; and silanols).  Suitable silicone emulsions include E2175 high viscosity polydimethylsiloxane (a 60% siloxane emulsion commercially available from Lambent Technologies, Inc.),
E21456 FG food grade intermediate viscosity polydimethylsiloxane (a 35% siloxane emulsion commercially available from Lambent Technologies, Inc.), HV490 high molecular weight hydroxy-terminated dimethyl silicone (an anionic 30-60% siloxane emulsion
commercially available from Dow Coming Corporation), SM2135 polydimethylsiloxane (a nonionic 50% siloxane emulsion commercially available from GE Silicones) and SM2167 polydimethylsiloxane (a cationic 50% siloxane emulsion commercially available from GE
Silicones.  Other water-miscible silicone materials include finely divided silicone powders such as the TOSPEARL.TM.  series (commercially available from Toshiba Silicone Co.  Ltd.); and silicone surfactants such as SWP30 anionic silicone surfactant,
WAXWS-P nonionic silicone surfactant, QUATQ-400M cationic silicone surfactant and 703 specialty silicone surfactant (all commercially available from Lambent Technologies, Inc.).  Preferred silicone emulsions typically contain from about 30 wt. % to about
70 wt. % water.  Non-water-miscible silicone materials (e.g., non-water-soluble silicone fluids and non-water-dispersible silicone powders) can also be employed in the lubricant if combined with a suitable emulsifier (e.g., nonionic, anionic or cationic
emulsifiers).  For applications involving plastic containers (e.g., PET beverage bottles), care should be taken to avoid the use of emulsifiers or other surfactants that promote environmental stress cracking in plastic containers when evaluated using the
PET Stress Crack Test set out below.  Polydimethylsiloxane emulsions are preferred silicone materials.  Preferably the lubricant composition is substantially free of surfactants aside from those that may be required to emulsify the silicone compound
sufficiently to form the silicone emulsion.


A variety of water-miscible lubricants can be employed in the lubricant compositions, including hydroxy-containing compounds such as polyols (e.g., glycerol and propylene glycol); polyalkylene glycols (e.g., the CARBOWAX.TM.  series of
polyethylene and methoxypolyethylene glycols, commercially available from Union Carbide Corp.); linear copolymers of ethylene and propylene oxides (e.g., UCON.TM.  50-HB-100 water-soluble ethylene oxide:propylene oxide copolymer, commercially available
from Union Carbide Corp.); and sorbitan esters (e.g., TWEEN.TM.  series 20, 40, 60, 80 and 85 polyoxyethylene sorbitan monooleates and SPAN.TM.  series 20, 80, 83 and 85 sorbitan esters, commercially available from ICI Surfactants).  Other suitable
water-miscible lubricants include phosphate esters, amines and their derivatives, and other commercially available water-miscible lubricants that will be familiar to those skilled in the art.  Derivatives (e.g., partial esters or ethoxylates) of the
above lubricants can also be employed.  For applications involving plastic containers, care should be taken to avoid the use of water-miscible lubricants that might promote environmental stress cracking in plastic containers when evaluated using the PET
Stress Crack Test set out below.  Preferably the water-miscible lubricant is a polyol such as glycerol.


If water is employed in the lubricant compositions, preferably it is deionized water.  Suitable hydrophilic diluents include alcohols such as isopropyl alcohol.  For applications involving plastic containers, care should be taken to avoid the use
of water or hydrophilic diluents containing contaminants that might promote environmental stress cracking in plastic containers when evaluated using the PET Stress Crack Test set out below.


Preferred amounts for the silicone material, hydrophilic lubricant and optional water or hydrophilic diluent are about 0.05 to about 12 wt. % of the silicone material (exclusive of any water or other hydrophilic diluent that may be present if the
silicone material is, for example, a silicone emulsion), about 30 to about 99.95 wt. % of the hydrophilic lubricant, and 0 to about 69.95 wt. % of water or hydrophilic diluent.  More preferably, the lubricant composition contains about 0.5 to about 8 wt.
% of the silicone material, about 50 to about 90 wt. % of the hydrophilic lubricant, and about 2 to about 49.5 wt. % of water or hydrophilic diluent.  Most preferably, the lubricant composition contains about 0.8 to about 4 wt. % of the silicone
material, about 65 to about 85 wt. % of the hydrophilic lubricant, and about 11 to about 34.2 wt. % of water or hydrophilic diluent.


The lubricant compositions can contain additional components if desired.  For example, the compositions can contain adjuvants such as conventional waterborne conveyor lubricants (e.g., fatty acid lubricants), antimicrobial agents, colorants, foam
inhibitors or foam generators, cracking inhibitors (e.g., PET stress cracking inhibitors), viscosity modifiers, film forming materials, antioxidants or antistatic agents.  The amounts and types of such additional components will be apparent to those
skilled in the art.


For applications involving plastic containers, the lubricant compositions preferably have a total alkalinity equivalent to less than about 100 ppm CaCO.sub.3, more preferably less than about 50 ppm CaCO.sub.3, and most preferably less than about
30 ppm CaCO.sub.3, as measured in accordance with Standard Methods for the Examination of Water and Wastewater, 18.sup.th Edition, Section 2320, Alkalinity.


The lubricant compositions preferably have a coefficient of friction (COF) that is less than about 0.14, more preferably less than about 0.1, when evaluated using the Short Track Conveyor Test described below.


A variety of kinds of conveyors and conveyor parts can be coated with the lubricant composition.  Parts of the conveyor that support or guide or move the containers and thus are preferably coated with the lubricant composition include belts,
chains, gates, chutes, sensors, and ramps having surfaces made of fabrics, metals, plastics, composites, or combinations of these materials.


The lubricant composition can also be applied to a wide variety of containers including beverage containers; food containers; household or commercial cleaning product containers; and containers for oils, antifreeze or other industrial fluids. 
The containers can be made of a wide variety of materials including glasses; plastics (e.g., polyolefins such as polyethylene and polypropylene; polystyrenes; polyesters such as PET and polyethylene naphthalate (PEN); polyamides, polycarbonates; and
mixtures or copolymers thereof); metals (e.g., aluminum, tin or steel); papers (e.g., untreated, treated, waxed or other coated papers); ceramics; and laminates or composites of two or more of these materials (e.g., laminates of PET, PEN or mixtures
thereof with another plastic material).  The containers can have a variety of sizes and forms, including cartons (e.g., waxed cartons or TETRAPACK.TM.  boxes), cans, bottles and the like.  Although any desired portion of the container can be coated with
the lubricant composition, the lubricant composition preferably is applied only to parts of the container that will come into contact with the conveyor or with other containers.  Preferably, the lubricant composition is not applied to portions of
thermoplastic containers that are prone to stress cracking.  In a preferred embodiment of the invention, the lubricant composition is applied to the crystalline foot portion of a blow-molded, footed PET container (or to one or more portions of a conveyor
that will contact such foot portion) without applying significant quantities of lubricant composition to the amorphous center base portion of the container.  Also, the lubricant composition preferably is not applied to portions of a container that might
later be gripped by a user holding the container, or, if so applied, is preferably removed from such portion prior to shipment and sale of the container.  For some such applications the lubricant composition preferably is applied to the conveyor rather
than to the container, in order to limit the extent to which the container might later become slippery in actual use.


The lubricant composition can be a liquid or semi-solid at the time of application.  Preferably the lubricant composition is a liquid having a viscosity that will permit it to be pumped and readily applied to a conveyor or containers, and that
will facilitate rapid film formation whether or not the conveyor is in motion.  The lubricant composition can be formulated so that it exhibits shear thinning or other pseudo-plastic behavior, manifested by a higher viscosity (e.g., non-dripping
behavior) when at rest, and a much lower viscosity when subjected to shear stresses such as those provided by pumping, spraying or brushing the lubricant composition.  This behavior can be brought about by, for example, including appropriate types and
amounts of thixotropic fillers (e.g., treated or untreated fumed silicas) or other rheology modifiers in the lubricant composition.  The lubricant coating can be applied in a constant or intermittent fashion.  Preferably, the lubricant coating is applied
in an intermittent fashion in order to minimize the amount of applied lubricant composition.  For example, the lubricant composition can be applied for a period of time during which at least one complete revolution of the conveyor takes place. 
Application of the lubricant composition can then be halted for a period of time (e.g., minutes or hours) and then resumed for a further period of time (e.g., one or more further conveyor revolutions).  The lubricant coating should be sufficiently thick
to provide the desired degree of lubrication, and sufficiently thin to permit economical operation and to discourage drip formation.  The lubricant coating thickness preferably is maintained at at least about 0.0001 mm, more preferably about 0.001 to
about 2 mm, and most preferably about 0.005 to about 0.5 mm.


Application of the lubricant composition can be carried out using any suitable technique including spraying, wiping, brushing, drip coating, roll coating, and other methods for application of a thin film.  If desired, the lubricant composition
can be applied using spray equipment designed for the application of conventional aqueous conveyor lubricants, modified as need be to suit the substantially lower application rates and preferred non-dripping coating characteristics of the lubricant
compositions used in the invention.  For example, the spray nozzles of a conventional beverage container lube line can be replaced with smaller spray nozzles or with brushes, or the metering pump can be altered to reduce the metering rate.


The lubricant compositions can if desired be evaluated using a Short Track Conveyor Test and a PET Stress Crack Test.


Short Track Conveyor Test


A conveyor system employing a motor-driven 83 mm wide by 6.1 meter long REXNORD.TM.  LF polyacetal thermoplastic conveyor belt is operated at a belt speed of 30.48 meters/minute.  Six 2-liter filled PET beverage bottles are stacked in an
open-bottomed rack and allowed to rest on the moving belt.  The total weight of the rack and bottles is 16.15 Kg.  The rack is held in position on the belt by a wire affixed to a stationary strain gauge.  The force exerted on the strain gauge during belt
operation is recorded using a computer.  A thin, even coat of the lubricant composition is applied to the surface of the belt using an applicator made from a conventional bottle wash brush.  The belt is allowed to run for 25 to 90 minutes during which
time a consistently low COF is observed.  The COF is calculated on the basis of the measured force and the mass of the bottles, averaged over the run duration.


PET Stress Crack Test


Standard 2-liter PET beverage bottles (commercially available from Constar International) are charged with 1850 g of chilled water, 31.0 g of sodium bicarbonate and 31.0 g of citric acid.  The charged bottle is capped, rinsed with deionized water
and set on clean paper towels overnight.  The bottoms of 12 bottles are dipped in a 200 g sample of the undiluted lube in a 125.times.65 mm crystal dish, then placed in a bin and stored in an environmental chamber at 37.8.degree.  C., 90% relative
humidity for 14 days.  The bottles are removed from the chamber, observed for crazes, creases and crack patterns on the bottom.  The aged bottles are compared with 12 control bottles that were exposed to a standard dilute aqueous lubricant (LUBODRIVE.TM. RX, commercially available from Ecolab) prepared as follows.  A 1.7 wt. % solution of the LUBODRIVE lubricant (in water containing 43 ppm alkalinity as CaCO.sub.3) was foamed for several minutes using a mixer.  The foam was transferred to a lined bin and
the control bottles were dipped in the foam.  The bottles were then aged in the environmental chamber as outlined above.


The invention can be better understood by reviewing the following examples.  The examples are for illustration purposes only, and do not limit the scope of the invention.


EXAMPLE 1


77.2 parts of a 96 wt. % glycerol solution, 20.7 parts deionized water, and 2.1 parts E2175 high viscosity polydimethylsiloxane (60% siloxane emulsion commercially available from Lambent Technologies, Inc.) were combined with stirring until a
uniform mixture was obtained.  The resulting lubricant composition was slippery to the touch and readily could be rinsed from surfaces using a plain water wash.  Using the Short Track Conveyor Test, about 20 g of the lubricant composition was applied to
the moving belt over a 90 minute period.  The observed COF was 0.062.  In a comparison Short Track Conveyor test performed using a dilute aqueous solution of a standard conveyor lubricant (LUBODRIVE.TM.  RX, commercially available from Ecolab, applied
using a 0.5% dilution in water and about an 8 liter/hour spray application rate), the observed COF was 0.126, thus indicating that the lubricant composition of the invention provided reduced sliding friction.


The lubricant composition of Example 1 was also evaluated using the PET Stress Crack Test.  The aged bottles exhibited infrequent small, shallow crazing marks.  For the comparison dilute aqueous lubricant, frequent medium depth crazing marks and
infrequent deeper crazing marks were observed.  No bottles leaked or burst for either lubricant, but the bottoms of bottles lubricated with a lubricant composition of the invention had a better visual appearance after aging.


EXAMPLE 2


Using the method of Example 1, 77.2 parts of a 96 wt. % glycerol solution, 20.7 parts deionized water, and 2.1 parts HV490 high molecular weight hydroxy-terminated dimethyl silicone (anionic 30-60% siloxane emulsion commercially available from
Dow Coming Corporation) were combined with stirring until a uniform mixture was obtained.  The resulting lubricant composition was slippery to the touch and readily could be rinsed from surfaces using a plain water wash.  Using the Short Track Conveyor
Test, about 20 g of the lubricant composition was applied to the moving belt over a 15 minute period.  The observed COF was 0.058.


EXAMPLE 3


Using the method of Example 1, 75.7 parts of a 96 wt. % glycerol solution, 20.3 parts deionized water, 2.0 parts HV490 high molecular weight hydroxy-terminated dimethyl silicone (anionic 30-60% siloxane emulsion commercially available from Dow
Corning Corporation) and 2.0 parts GLUCOPON.TM.  220 alkyl polyglycoside surfactant (commercially available from Henkel Corporation) were combined with stirring until a uniform mixture was obtained.  The resulting lubricant composition was slippery to
the touch and readily could be rinsed from surfaces using a plain water wash.  Using the Short Track Conveyor Test, about 20 g of the lubricant composition was applied to the moving belt over a 15 minute period.  The observed COF was 0.071.


EXAMPLE 4


Using the method of Example 1, 72.7 parts of a 99.5 wt. % glycerol solution, 23.3 parts deionized water, 2 parts HV495 silicone emulsion (commercially available from Dow Corning Corporation) and 2 parts GLUCOPON.TM.  220 alkyl polyglycoside
surfactant (commercially available from Henkel Corporation) were combined with stirring until a uniform mixture was obtained.  The resulting lubricant composition was slippery to the touch and readily could be rinsed from surfaces using a plain water
wash.  However, the presence of the surfactant caused an increase in stress cracking in the PET Stress Crack Test.


Various modifications and alterations of this invention will be apparent to those skilled in the art without departing from the scope and spirit of the invention, and are intended to be within the scope of the following claims.


* * * * *























				
DOCUMENT INFO
Description: This invention relates to conveyor lubricants and to a method for conveying articles. The invention also relates to conveyor systems and containers wholly or partially coated with such lubricant compositions.BACKGROUND ARTIn commercial container filling or packaging operations, the containers typically are moved by a conveying system at very high rates of speed. Copious amounts of aqueous dilute lubricant solutions (usually based on fatty acid amines) aretypically applied to the conveyor or containers using spray or pumping equipment. These lubricant solutions permit high-speed operation of the conveyor and limit marring of the containers or labels, but also have some disadvantages. For example,aqueous conveyor lubricants based on fatty amines typically contain ingredients that can react with spilled carbonated beverages or other food or liquid components to form solid deposits. Formation of such deposits on a conveyor can change the lubricityof the conveyor and require shutdown to permit cleanup. Some aqueous conveyor lubricants are incompatible with thermoplastic beverage containers made of polyethylene terephthalate (PET) and other plastics, and can cause environmental stress cracking(crazing and cracking that occurs when the plastic polymer is under tension) in plastic containers. Dilute aqueous lubricants typically require use of large amounts of water on the conveying line, which must then be disposed of or recycled, and whichcauses an unduly wet environment near the conveyor line. Moreover, some aqueous lubricants can promote the growth of microbes.SUMMARY OF THE INVENTIONThe present invention provides, in one aspect, a method for lubricating the passage of a container along a conveyor comprising applying a mixture of a water-miscible silicone material and a water-miscible lubricant to at least a portion of thecontainer-contacting surface of the conveyor or to at least a portion of the conveyor-contacting surface of the container.The present invention